Date:   Wed, 16 May 2018 08:29:02 -0700
From:   syzbot <syzbot+769a7ccbbb4b5074f125@...kaller.appspotmail.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, yoshfuji@...ux-ipv6.org
Subject: INFO: rcu detected stall in ip_route_output_key_hash

Hello,

syzbot found the following crash on:

HEAD commit:    0b7d9978406f Merge branch 'Microsemi-Ocelot-Ethernet-switc..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1138c477800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b632d8e2c2ab2c1
dashboard link: https://syzkaller.appspot.com/bug?extid=769a7ccbbb4b5074f125
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+769a7ccbbb4b5074f125@...kaller.appspotmail.com

netlink: 4 bytes leftover after parsing attributes in process  
`syz-executor2'.
random: crng init done
INFO: rcu_sched self-detected stall on CPU
	1-...!: (121515 ticks this GP) idle=e7e/1/4611686018427387908  
softirq=31362/31362 fqs=7
	 (t=125000 jiffies g=16439 c=16438 q=668508)
rcu_sched kthread starved for 124958 jiffies! g16439 c16438 f0x2  
RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0
RCU grace-period kthread stack dump:
rcu_sched       R  running task    23768     9      2 0x80000000
Call Trace:
  context_switch kernel/sched/core.c:2848 [inline]
  __schedule+0x801/0x1e30 kernel/sched/core.c:3490
  schedule+0xef/0x430 kernel/sched/core.c:3549
  schedule_timeout+0x138/0x240 kernel/time/timer.c:1801
  rcu_gp_kthread+0x6b5/0x1940 kernel/rcu/tree.c:2231
  kthread+0x345/0x410 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
NMI backtrace for cpu 1
CPU: 1 PID: 4488 Comm: syz-fuzzer Not tainted 4.17.0-rc4+ #45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
  nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
  trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline]
  rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1376
  print_cpu_stall kernel/rcu/tree.c:1525 [inline]
  check_cpu_stall.isra.61.cold.80+0x36c/0x59a kernel/rcu/tree.c:1593
  __rcu_pending kernel/rcu/tree.c:3356 [inline]
  rcu_pending kernel/rcu/tree.c:3401 [inline]
  rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763
  update_process_times+0x2d/0x70 kernel/time/timer.c:1636
  tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
  tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
  __run_hrtimer kernel/time/hrtimer.c:1398 [inline]
  __hrtimer_run_queues+0x3e3/0x10a0 kernel/time/hrtimer.c:1460
  hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
  smp_apic_timer_interrupt+0x15d/0x710 arch/x86/kernel/apic/apic.c:1050
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
RIP: 0010:rcu_is_watching+0x6/0x140 kernel/rcu/tree.c:1071
RSP: 0000:ffff8801daf06620 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
RAX: ffff8801ad526240 RBX: 0000000000000000 RCX: ffffffff86444456
RDX: 0000000000000100 RSI: ffffffff864444b8 RDI: 0000000000000001
RBP: ffff8801daf06628 R08: ffff8801ad526240 R09: 0000000000000002
R10: ffff8801ad526240 R11: 0000000000000000 R12: 1ffff1003b5e0cca
R13: ffff88008ff1a100 R14: 0000000000000000 R15: ffff8801daf066d0
  rcu_read_unlock include/linux/rcupdate.h:684 [inline]
  ip_route_output_key_hash+0x2cd/0x390 net/ipv4/route.c:2303
  __ip_route_output_key include/net/route.h:124 [inline]
  ip_route_output_flow+0x28/0xc0 net/ipv4/route.c:2557
  ip_route_output_key include/net/route.h:134 [inline]
  sctp_v4_get_dst+0x50e/0x17a0 net/sctp/protocol.c:447
  sctp_transport_route+0x132/0x360 net/sctp/transport.c:303
  sctp_packet_config+0x926/0xdd0 net/sctp/output.c:118
  sctp_outq_select_transport+0x2bb/0x9c0 net/sctp/outqueue.c:877
  sctp_outq_flush_ctrl.constprop.12+0x2ad/0xe60 net/sctp/outqueue.c:911
  sctp_outq_flush+0x2ef/0x3430 net/sctp/outqueue.c:1203
  sctp_outq_uncork+0x6a/0x80 net/sctp/outqueue.c:776
  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1820 [inline]
  sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline]
  sctp_do_sm+0x596/0x7160 net/sctp/sm_sideeffect.c:1191
  sctp_generate_heartbeat_event+0x218/0x450 net/sctp/sm_sideeffect.c:406
  call_timer_fn+0x230/0x940 kernel/time/timer.c:1326
  expire_timers kernel/time/timer.c:1363 [inline]
  __run_timers+0x79e/0xc50 kernel/time/timer.c:1666
  run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692
  __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x1d1/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:525 [inline]
  smp_apic_timer_interrupt+0x17e/0x710 arch/x86/kernel/apic/apic.c:1052
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
  </IRQ>
RIP: 0033:0x40b55d
RSP: 002b:000000c424bedca8 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13
RAX: 000000c4244e5470 RBX: 000000004d36768c RCX: 0000000000000000
RDX: 000000c4244e5470 RSI: 000000000000ffff RDI: 0000000000000000
RBP: 000000c424bedcc0 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000009466f2 R11: 0000000000000004 R12: 0000000000000000
R13: 0000000000000020 R14: 0000000000000013 R15: 0000000000000034
BUG: workqueue lockup - pool cpus=0 node=0 flags=0x0 nice=0 stuck for 125s!
BUG: workqueue lockup - pool cpus=0-1 flags=0x4 nice=0 stuck for 125s!
Showing busy workqueues and worker pools:
workqueue events: flags=0x0
   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=3/256
     in-flight: 2104:do_numa_crng_init
     pending: drbg_async_seed, cache_reap
   pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=9/256
     pending: defense_work_handler, defense_work_handler,  
defense_work_handler, defense_work_handler, defense_work_handler,  
defense_work_handler, check_corruption, vmstat_shepherd, cache_reap
workqueue events_power_efficient: flags=0x80
   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
     pending: do_cache_clean
   pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=2/256
     pending: check_lifetime, gc_worker
workqueue writeback: flags=0x4e
   pwq 4: cpus=0-1 flags=0x4 nice=0 active=1/256
     in-flight: 6:wb_workfn
workqueue ipv6_addrconf: flags=0x40008
   pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/1
     pending: addrconf_verify_work
workqueue krdsd: flags=0xe000a
   pwq 4: cpus=0-1 flags=0x4 nice=0 active=1/1
     in-flight: 43:rds_connect_worker
pool 2: cpus=1 node=0 flags=0x0 nice=0 hung=0s workers=4 idle: 24 1980 18
pool 4: cpus=0-1 flags=0x4 nice=0 hung=0s workers=7 idle: 22 8018 287 6751  
89


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